The present invention relates to an electric leaner for use in households and/or industry.
In recent years, carpets are often used as a floor covering material. In order to suck up dust in the pile of the carpets, electric cleaners have been required to employ larger motors to create a larger suction power.
Furthermore, the speed of the blower motor contained within the electric cleaner, is selectively controlled by a control unit in the handle that is attached to the end of the flexible hose, in accordance with the material being cleaned so that the cleaning can be achieved with the appropriate suction-air volume to save electricity and minimize noise.
In another electric cleaner, a dust sensor is provided in the air channel between the suction opening and the dust collecting apparatus, and the speed of the blower motor is automatically increased upon the detection of the dust by the dust sensor.
Such a conventional electric cleaner will be described hereinafter with reference to the drawings.
FIG. 4 shows an electrical circuit diagram of a conventional electric cleaner, a variable resistor 1, installed in the control unit in the handle which is attached to the end of a flexible hose, is used to variably control the speed of the blower motor 2. A gate signal generated in the phase control circuit 3, is varied by the resistance value of the variable resistor 1. By means of the gate signal, a bidirectional thyristor 4 varies a conductive angle with respect to the blower motor 2 of the AC power supply 5, and thereby varies the speed of the blower motor 2. A pair of contacts employed in an electromagnetic relay 6 are closed upon receiving a dust detection signal transmitted from a dust sensor unit 7, so as to bypass the variable resistor 1. A current-limiting resistor 9 is for a light emitting diode 8 (hereinafter referred to as an LED). A phototransistor 10 is used to change the intensity of the light emitted by the LED 8 into a current variation. The dust sensor circuit 7 detects the above said current variation and outputs the dust detecting signal. A load resistor 11 is used for the phototransistor 10.
An electric cleaner as described above operates in a manner as described below.
To begin with, by the sliding of the knob 18 (see FIG. 6) which is connected to the variable resistor 1 built-in within the control unit in the handle 14, the electric current which is phase controlled by the phase control circuit 3, is supplied to the blower motor through the bidirectional thyristor 4 and the blower motor 2 rotates at the desired speed for the cleaning purposes.
In the case of this example, as the resistance value of the variable resistor 1 increases, the speed of the blower motor 2 goes down and if the resistance value of the variable resistor 1 becomes equal to zero, then the blower motor 2 runs at its maximum speed. Accordingly, by the operation of the variable resistor 1 in accordance with the material being cleaned, a suction-air volume suitable to the material being cleaned is obtained.
When the dust sucked in through the suction nozzle 12, passes through a dust sensor unit 17 (see FIG. 5) consisting of the LED 8 and phototransistor 10, the light emitted by the LED 8 is interrupted and does not reach the phototransistor 10. Then, the dust sensor circuit 7 energizes the electromagnetic relay 6 and the pair of contacts thereof are closed. Upon the closing of the contacts, the variable resistor 1 is bypassed and the blower motor 2 runs at its maximum speed. Furthermore, at a given time (e.g.--three seconds in the case of a conventional electric cleaner) after the dust passing through the dust sensor unit 17 is no longer present, the dust sensor circuit 7 turns off the electromagnetic relay 6, and the pair of contacts opens, and the speed of the blower motor 2 returns to the one originally established by the variable resistor 1. The operation pattern of the blower motor 2 is shown in FIG. 3(C).
However, in such a conventional construction as described hereinabove, when the dust is sucked in during the cleaning of a curtain with the knob 18 set to the position of "curtain", that is, the run the blower motor 2 at its minimum speed, the speed of the blower motor 2 suddenly goes up and reaches its maximum speed with the problems that the suction nozzle sucks in the curtain, thus resulting in an operational problem.